(1) Field of the Invention
The invention relates to a method of curing a spin-on-glass (SOG) planarization layer for an integrated circuit device, and more particularly, to a method of curing a spin-on-glass (SOG) planarization layer of an integrated circuit via ion implantation.
(2) Description of the Prior Art
The spin-on-glass materials and how they are processed may be critical to the success of the process for planarization of integrated circuits. The most useful materials are silicates--Si(OH).sub.4 and siloxanes--(RO)nSi(OH).sub.4-n. These types of materials are generally known and available. Examples of the silicate type is OCD Type 2 made by Tokyo Okha Corp. and siloxane type is OCD Type 6 made by Tokyo Okha Corp. Each spin-on-glass coating is less than about 0.3 micrometers and preferably between about 0.08 and 0.2 micrometers. The more coatings that are used, the better the planarity. The material to be applied is thoroughly mixed in a suitable solvent which is usually a combination of a high boiling point solvent and a low boiling point solvent.
The preferred low boiling point solvents are methanol, ethanol, and propanol. The middle boiling point solvents are buthanol, penthanol, hexanol and methyl cellosolve. The high boiling point solvents are butyl cellosolve, propylene glycol, diethylene glycol and Carbindol. Other potential vehicles or solvents are NMP, HMPA, N.N-dimethylacetoamide, acetyl acetone, and malonic acid diethylester and the like.
The spin-on-glass material suspended in the vehicle or solvent is deposited onto the semiconductor wafer surface and uniformly spread thereover by the action of spinning the wafer. The material fills the indentations in the integrated circuit wafer surface, that is planarization. Most of the vehicle or solvent is driven off by a low temperature baking step. At this point, the critical vacuum degassing step is accomplished by subjecting the wafer to a vacuum of less than about 100 mtorr and 350 degrees C. This last step removes chemical materials which could during latter processing cause cracking and corrosion of the next level conductor material. Other coatings of the spin-on-glass material are applied, baked and vacuum degassed until the desired spin-on-glass layer is formed.
The final step in the making of the spin-on-glass layer is curing. Curing is a high temperature heating step to cause the breakdown of the silicate or siloxane material to a silicon dioxide like cross linked material. U.S. Pat. No. 4,983,546 filed on Dec. 20, 1989 by Il S. Hyun et al describes a method of applying an ultraviolet light source within a heating chamber to cure the spin-on-glass layer.
The conventional curing methods for spin-on-glass present problems. Gases trapped within the spin-on-glass after curing integrated circuit can cause corrosion of the metal conductors in time. Additionally, the etch rate of furnace-cured spin-on-glass is poor compared to the etch rate of thermally grown oxide.